STUDIES ON PROACTIVATOR ACTIVITY IN HUMAN BLOOD

Plasminogen and proactivator were measured in the euglobulin fraction of serum and citrate plasma. Plasminogen was measured by activation with urokinase, followed by caseinolysis. Proactivator was measured by incubation with streptokinase and porcine plasminogen (which did not contain pro-activator), followed by caseinolysis. On the average, serum contained 89 per cent of the plasminogen in plasma, but only 59 per cent of the proactivator in plasma. Proactivator activity decreased slightly after acidification of plasma euglobulin. From heat stability experiments it is suggested that euglobulin contains an acid-and heat-labile inhibiting activity against the activation of plasminogen by streptokinase. © 1969 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted.